Metastable Phase Formation from Nd-Dy-Fe-B Undercooled Melt

Abstract

Abstract Nd 10-x Dy x Fe 85 B 5 (x = 0-3) alloy samples were melted and then solidified in the containerless state of a drop tube at oxygen partial pressure of 10 -1 Pa. The calculated cooling rate of the spherical sample was over 10 3 K/s. The Nd 10 Fe 85 B 5 sample consists of the Nd 2 Fe 17 B x metastable phase together with the α-Fe dendrite. The metastable phase was partially decomposed into small grains of Nd 2 Fe 14 B and α-Fe phases by a solid state decomposition reaction. The substitution of Dy for Nd in the range from 10 to 20 atomic percent was effective to suppress the primary formation of the α-Fe dendrite and to promote the formation of the RE 2 Fe 17 B x metastable phase. When the substitution rate of Dy increased to 30 atomic percent, a large amount of the α-Fe dendrite was formed because an oxide layer of rare earth elements was generated at the sample surface due to the easy oxidization tendency of Dy